Various noise cancellation and reduction techniques, both active and passive, have been used to reduce unwanted ambient sounds. For example, an active system includes a speaker producing sound with the same amplitude but with the opposite polarity to the ambient sound. The system is designed such that the ambient and generated waves cancel each other thereby producing noise cancellation. However, active noise cancellation in free space has been challenging and generally limited to narrow frequency ranges. Furthermore, active noise reduction using conventional feedback methods tends to cause amplification of the noise at other frequencies. What is needed are methods and system for broad-band active noise cancellation.